The invention pertains to a suspension of an injection preparation for sealing and/or decreasing the penetrability of soil (loose rock) and/or solid rock and/or construction sites to penetration by fluids, especially water or gases. The invention is especially useful for sealing the bottom of sandy subsoil in excavations or for the sealing of fissures or cracks in solid rock.
In civil engineering projects in sandy subsoil, the penetration of groundwater into excavations must be avoided. Generally, the groundwater inflow is intercepted by vertically surrounding the excavations with a sealed or narrow wall. The back pressure of the groundwater from the subsoil is interrupted by injections into the soil with injection solutions or injection suspensions wherein the injection is done according to a certain pattern.
The solids of the injection preparation suspension should have a particle size that allows them to penetrate into the smallest cavities. Moreover, the injection preparation suspension must assure that after a socalled maturing time, the penetration of water into the injected sediment is at least extensively and adequately reduced. The environment must not be endangered as a result of the injected materials. The injection process must be easy and economical to execute.
It is known to use injection solutions in the form of socalled "soft gels" or ultrafine cement suspensions.
Soft gels consist of solutions of water glass and a hardener component. The disadvantage with these is that the solution must be injected within a very short period of time after addition of the hardener because otherwise reactions occur that increase the viscosity of the injection suspension in such a manner that the injection cannot be done. In addition, disposal of the remainder of the suspension is problematic. Moreover, a very significant disadvantage is the undesirable permanent introduction of alkalis to the groundwater. For this reason, demands are already being made to exclude such soft gels from injection solutions.
Ultrafine cement suspensions consist of aqueous slurries of ultrafine cement with a very high degree of fineness to which sodium bentonite is usually added for stabilization. The ultrafine cement suspensions can be handled easily and are not hazardous. Ultrafine cements usually consist of ultrafine powdered metallurgical slag (blast furnace slag) and activators and/or portland cements which, after addition of water, temporarily have an alkaline reaction as a result of their hydration, with the liberation of Ca(OH).sub.2. The Ca(OH).sub.2 reacts with the CO.sub.2 of the groundwater to produce lime. In this respect, the injection process with ultrafine cement suspensions protects the environment.
Sodium bentonite is a clay that is capable of strong swelling which disintegrates into very small particles in aqueous suspension. The ultrafine sodium bentonite particles in a quiescent state impart a flow limit to suspensions that prevents the solid components from sedimenting. In the presence of hydrating cement, sodium bentonites tend towards a charge reversal of the ions, with undesired agglomeration as a consequence; the high degree of fineness of the starting components can therefore not be fully exploited. Moreover, the storage stability of sodium bentonitecement mixtures is very limited.
An additional disadvantage of sodium bentonitestabilized ultrafine cement suspensions is that the desired effect of the injection is impaired in saltcontaining soils. In addition, there is the fact that sodium bentoniteultrafine cement suspensions with high waterbinder values tend to leach into the subsoil, which can generally only be avoided if the proportion of sodium bentonite is substantially increased. However, with an increase in the proportion of sodium bentonite, the danger of agglomeration also increases.
U.S. Pat. No. 4,662,943 describes a mixture containing cement, at least one salt, and at least one polysaccharide or a mixture of polysaccharides that has a dissolution time of greater than 10 min. This binder mixture serves as a backfilling mixture based on a deepwell cement. The deepwell cement used in this is a Class H deepwell cement (as per API) with a normal degree of fineness that is stabilized with polysaccharides and salts. The mixture of U.S. Pat. No. 4,662,943 contains no inert mineral filler. However, according to the patent, heavy additives are proposed as fillers such as, e.g., hematite, ilmenite, quartz powder, and sand. These additives have the task of making the binder mixture heavier, i.e., to increase the bulk density as well as to act as blenders. The salt addition produces a certain property, the socalled "inverse rheology," i.e., that the viscosity of the suspension increases with increasing temperature.
U.S. Pat. No. 2,655,004 pertains to a mixture and a process for reinforcing and solidifying porous earth work, stone masonry work, construction concrete, etc. According to U.S. Pat. No. 2,655,044, an improved hardenable, cementcontaining mixture is formed that can be pressed into the cavities and fissures of a porous or holefilled concrete mass under pressure. An injection suspension as per this document contains hydraulic cement of normal particle size, water, and a small proportion of dispersant, wherein the dispersant is indicated as being cellulose ether. According to the description, inert fillers can additionally be present in the mixture.
EP 0,631,994 Al describes an injection suspension based on ultrafine binder and ultrafine filler, wherein hydroxyethylcellulose is used as a dispersant. Such a binder suspension has a waterbinder ratio of 0.672.3 for ultrafine binders and 0.335 for normal cements. According to this document, mica, talc, kaolin, calcite, feldspar, dolomite, silica, or titanium or aluminum oxide can be used as ultrafine fillers.
It is the goal of the invention to produce an injection preparation suspension with at least one binder that can be handled easily and assures optimal sealing or decreasing of the penetrability, wherein the injection preparation suspension has an increased stability towards sedimentation even at high watersolids values. This goal is attained by an injection preparation suspension as disclosed herein.